the cables are protected by nonmetallic conduit sleeves at the crossing.
The radius of bends in cables shall be not less than 12 times the diameter
of the cable. Cables shall not be left under longitudinal tension. The
first layer of backfill shall be 150 mm 6 inches thick and shall consist of
sand or stone-free earth. One-inch untreated planks, not less than 200 mm
8 inches in width, or approved equal protection, shall be placed end to end
along the cable run, approximately 75 mm 3 inches above the cable. A 0.127
mm (5 mil) 5 mil, brightly colored plastic tape not less than 75 mm 3 inches
in width and suitably inscribed at not more than 3 m 10 feet on centers, or
other approved dig-in warning indication, shall be placed approximately 300
mm 12 inches below finished grade levels of trenches. Selected backfill of
sand or stone-free earth shall be provided to a minimum depth of 75 mm 3
inches above cables.
3.4.3.2
Requirements for Installation in Duct
Where indicated on drawing, cable shall be installed in duct lines. Ground
and neutral conductors shall be installed in duct with the associated phase
conductors. The segments of direct-burial cable that cross under new
railroad tracks, roads, or paving exceeding 1.5 m 5 feet in width, shall be
installed in plastic, or rubber duct encased in concrete in accordance with
paragraph DUCT LINES. Pulling of cable into conduit from a fixed reel
position will be permitted. At interfaces with direct-burial cable, the
direct-burial cable shall be centered in the entrance to the duct, using an
approved waterproof, nonhardening mastic compound to facilitate the
centering. Where crossing existing railroad tracks, coated rigid steel
conduit shall be installed under the tracks, in lieu of concrete-encased
duct, in accordance with paragraph DUCT LINES. Installation shall be in
accordance with NFPA 70 and the regulations of the railroad.
3.4.3.3
Location of Cable Splices
Splices in direct-burial cable will not be permitted in runs of 150 m 500
feet or less or at intervals of less than 150 m 500 feet in longer runs
except as required for taps. Where cable splices in shorter intervals are
required to avoid obstructions or damage to the cable, the location shall
be as approved. Cable splices shall be installed in cable boxes or
concrete handholes.
3.4.3.4
Markers
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NOTE: Markers will be detailed on drawings in
accordance with TM 5-811-1/AFJMAN 32-1080.
**************************************************************************
Cable and cable splice markers shall be located near the ends of cables, at
each cable splice, approximately every 120 m 400 feet along the cable run,
and at changes in direction of the cable run. Markers need not be placed
along cables laid in relatively straight lines between lighting poles that
are spaced less than 120 m 400 feet apart. Markers shall be placed
approximately 600 mm 2 feet to the right of the cable or cable splice when
facing the longitudinal axis of the cable in the direction of the
electrical load. The marker shall be concrete with a 28 day compressive
strength of 17 MPa 2500 psi in accordance with Section 03300A CAST-IN-PLACE
STRUCTURAL CONCRETE. The letter "C" shall be impressed in the top of each
marker.
SECTION 16528A
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